The present invention relates to a method and a device for mounting a winding, on a stator for a generator as specified in the preamble of claim 1 and 6, respectively.
It is an object of the present invention to facilitate mounting when winding the stator. Another object of the invention is to provide a smooth and reliable laying of the conductor in the stator slots.
For these objects to be achieved, laying of the conductor should be carried out only with a xe2x80x9cdeadxe2x80x9d conductor, i.e. No torsional twist or a minimum of torsional twist of the conductor is allowed when it is inserted in the stator slot.
A conductor which is coiled onto a drum should be uncoiled or pulled off in order for it to be free from twist. It is important that the torsional twist resulting from coiling should be maintained in order for the result to be zero, i.e. Without any remaining twist on completion of the uncoiling or pulling off. By pulling off is meant a procedure which is similar to uncoiling, i.e. Not unwinding.
The laying of the conductor should be carried out in accordance with a winding diagram, which may be specific to each generator. The stator slots are normally numbered from 1 onwards, clockwise when viewed from the upper side of the stator. Positions in the stator slots (number of xe2x80x9cholesxe2x80x9d for the conductor) are numbered from 1 onwards with number 1 farthest away from the axle centre of the stator frame. The conductor is laid from slot X, position A to slot Y, position B and so on. Between these positions, the conductor is laid in the form of arcs of pretermined dimensions.
Conductor stiffness and diameter vary within the same generator depending on different voltage levels.
The outer semiconductive layer of the conductor might be soft and must not be damaged and the bending radius of the conductor must not fall below the minimum permissible.
The above described objects are achieved by the method according to the present invention, which is characterized by the following steps:
a) using cable for the winding, the winding being wound with a number of cables (K) of predetermined lengths for the intended winding of the stator,
b) placing the centre of the cable, i.e. the location at half the predetermined length, at the location of the stator slot representing the middle of an intended coil arc,
c) starting from the said centre of the coil arc, winding the first half cable length onto the stator in order to form a first coil arc half and part of the total stator winding, and
d) winding the remaining half cable length onto the stator, starting from the said centre of the coil arc and in the opposite direction to the winding of the first half cable length in order to form the other half of the coil arc on the stator and another part of the total stator winding.
The method may be realized by means of a device according to the present invention, said device being characterized by being arranged to be used for winding with cable comprising a number of cables (K) of predetermined lengths for the stator winding, which device comprises a drum means arranged to initially support the entire predetermined cable length, a first and a second cable feeder adjustable relative to the stator slots, which cable feeders are arranged to alternately lay the cable in successive stator slots in accordance with a predetermined winding diagram by means of intermediate storage means, so that first mounting of the first half of the said predetermined cable length is to be carried out starting from the stator slot representing the middle of an intended coil arc, and when winding of the first winding portion is completed, mounting of the second winding portion is to be carried out starting also from said stator slot.
The method implies that first one cable half is mounted, i.e. half the cable length is advanced through the stator slots and laid therein and thereafter the second half of the cable is advanced and laid. In particular the invented method and device are advantageous when used in connection with an rotating electric machine of the type as disclosed in WO-97/45919.
A cable intended for winding a stator according to the invention may be delivered wound onto a delivery drum. The method according to the present invention may in that case preferably be realized as follows: Unwinding a predetermined length from the delivery drum and coiling it onto a drum means. The cable is cut off when a predetermined length has been coiled onto the drum means. In connection with the coiling, a distinct marking is made at the cable centre, i.e. at half the predetermined cable length. The procedure continues in that a first half of the cable is once more uncoiled from the drum means so as to be mounted in the winding slots of the stator and is thereafter coiled onto an intermediate storage means, the centre marking of the cable being located such that the mark represents the middle of an intended coil arc. The cable is taken from the intermediate storage means, is mounted in winding slots and the rest of the cable is coiled onto the intermediate storage means. This continues until half the cable is mounted. The other cable half is still on the drum means. In the further procedure, the other cable half is uncoiled from the drum means so as to be mounted in the winding slots of the stator and then coiled onto the intermediate storage means. The cable is taken from the intermediate storage means, is mounted in the winding slots and the rest of the cable is coiled onto the intermediate storage means. This continues until the other half of the cable is also mounted.
The intermediate storage means may be formed of two separate capstans, which are used alternately when mounting the cable half in the stator slots, or the intermediate storage means may be formed of a dual drum capstan, the two drums of which are used alternately when mounting the cable half in the stator slots.
The drum means may be formed of a separate capstan machine or it may be formed as an additional drum, the coiling of which is arranged to take place by means of the intermediate storage means, which drum, however, during uncoiling is arranged separately from the intermediate storage means.
The laying of the cable may be carried out in accordance with two main principles: Pushing the cable into the stator slots using a cable feeder in accordance with Method 1 as described below or pulling the cable trough the slots using a pull wire in accordance with Method 2 as described below.
Method 1
The cable is disconnected from the first capstan and is pulled out over the drum edge thereof. For heavy cable, the pulling out may be carried out using a telpher or other facility. A cable guide is mounted on the free end of the cable. The cable guide consists of a cylindrical rod the diameter of which is somewhat smaller than that of the stator slot concerned and its length is about five times its diameter. The cable with cable guide is inserted in a first cable feeder which is located at one side of the stator frame (the upper side). The cable is run by means of the first cable feeder through the stator slot and out thereof on the other side of the stator frame (the under side), where the cable with cable guide, when a sufficient cable length has been advanced, is inserted in a second cable feeder, which is disposed at the other side of the stator frame and is directed towards a successive stator slot in accordance with a predermined winding diagram, so that by means of this second cable feeder the cable is run through said successive stator slot and out thereof on the said one side of the stator frame (the upper side). Here the first cable feeder, which has been directed towards yet another stator slot in accordance with the said diagram, now takes over the cable with cable guide for further transport. It may be necessary to temporarily stop one cable feeder while the other cable feeder advances the cable in a stator slot. The cable feeders are thus driven alternately or simultaneously until the centre marking of the cable gets into a position just opposite the stator slot representing the middle of the coil arc (towards which the first cable feeder was directed at the start).
To achieve the required arc dimension, the cable feeder which has pushed the cable into a stator slot is disconnected and moved. Instead, the cable feeder on the opposite side of the stator frame is connected, which will pull the cable until the required arc dimension is reached.
The work proceeds in accordance with the above mentioned principle, i.e. insertion in one stator slot and return feed in another in accordance with the winding diagram. The free cable end is fed into the intermediate storage means on the capstan or drum which is empty at the time, every other time the first capstan or drum and every other time the other capstan or drum. The arc portions are adjusted continuously by means of the cable feeders.
When the first half of the cable is mounted, the procedure is repeated with the second half of the cable.
The method and the device are special, however, are not exclusively intended to be applied when mounting high-voltage cable on a generator where high-voltage cable is used in the windings of the stator, which cable lacks the outer protective covering normally surrounding it.
The cable is preferably of the kind consisting of an inner core with a plurality of wires, an inner semiconductive layer surrounding the core, an insulating layer surrounding the inner semiconductive layer, and an outer semiconductive layer surrounding the insulating layer, preferably with a diameter of about 20 to 200 mm and a conductor area ranging from 80 to 3000 mm2.
Method 2
The cable is disconnected from the first capstan and is pulled out over the drum edge thereof. For a heavy cable, the pulling out may take place by means of a telpher or other facility. A pull wire is mounted to the free end of the cable.
The pull wire suitably consists of a flexible fibre glass rod having a smaller diameter than that of the cable. At one end of the pull wire, a sleeve with attachment for connection of the cable is provided.
The pull wire is inserted manually into the stator slot from one side of the stator frame (the upper side) and is taken out thereof on the opposite side (the under side). The pull wire is thereafter inserted in a first cable feeder disposed at the said opposite side of the stator frame. The pull wire with cable is pulled through the stator slot and when a sufficient length has been advanced, the pull wire is inserted in the next stator slot according to the winding diagram. When a sufficient length of the pull wire has been advanced from the said next stator slot at one side of the stator frame (the upper side) it is inserted in another cable feeder disposed there for pulling the cable through the stator slot.
Similarly as in Method 1 it may be necessary to temporarily stop one cable feeder while the other cable feeder pulls the cable in a stator slot. The cable feeders are thus driven alternately or simultaneously until the centre marking of the cable is at a location opposite the stator slot representing the middle of the coil arc (towards which the first cable feeder was directed at the start).
In order to achieve the required arc dimension, the cable feeder that has pulled the cable into a stator slot is disconnected and moved. Instead, the cable feeder on the opposite side of the stator frame is connected, which will pull the cable until the required arc dimension is reached.
The work proceeds in accordance with the above mentioned principle, i.e. pulling through one stator slot and return feed through another in accordance with the winding diagram. The free cable end is fed into the intermediate storage means on the capstan or drum which is empty at the time, every other time the first capstan or drum and every other time the other capstan or drum. The arc portions are continuously adjusted by means of the cable feeders.
When the first half of the cable is mounted, the procedure is repeated with the other cable half.